The standard specifications for operation of Ethernet OAM (Operation, Administration and Management) circuits, and particularly those conforming to IEEE 802.1ag and ITU-T Y.1731, include a check for connectivity between two management endpoints (MEPs) in a management domain (MD). The management endpoints perform the check by means of the periodic transmission of connectivity check messages (CCMs) to each other. Both endpoints determine whether they have received a valid CCM within a prescribed time. The period, i.e. the interval between CCM transmissions, can be, under current specifications, any one of eight values starting from 3.3 ms up to 10 minutes. The period may be configured, i.e. selected for each connection. A connectivity error is reported by an endpoint when a CCM has not been received from the endpoint's partner within a set multiple (presently 3.5) of the CCM transmission interval. Thus, at the fastest CCM rate (3.3 ms), an error will be reported when a message from the partner is not received within 3.5×3.3=11.55 ms.
During the start-up of a link, connectivity errors may be reported incorrectly owing to the time lag of an operator enabling both ends of a link. For example, suppose that an operator programs an endpoint A for an OAM connection at a rate of 3.3 ms. This endpoint will commence the transmission of CCMs and simultaneously checking for CCMs. If there is a delay of more than 11.55 ms in the commencement of operation and, in particular, the transmission of CCMs by the link partner B, endpoint A will report erroneously.
The present exemplary embodiment aims to reduce the incidence of such false reporting.
The state of the art is exemplified by the documents IEEE Std 802.1ag-2007 pages 138-158, US 2005/0180419-A1 and EP-1416671-A2.